1. Field of the Invention
The present invention relates to catheter systems and, more specifically, infusion catheters having a tip opening and an occluding wire configured to selectively seal the tip opening closed.
2. The Relevant Technology
A reasonably common and dangerous medical condition arises when a blood clot develops in the vascular system of the body of a patient. A blood clot or thrombus can endanger the health of a patient in at least two significant ways. First, the clot may restrict or even completely stop essential blood flow to a portion of the patient's body. If the blood flow to the brain or heart for example is restricted the patient's life may be placed in jeopardy. Additionally, a clot may break loose from the site at which it formed and be carried by the blood stream to an organ, such as the heart, where it may cause irreparable damage or even death. Accordingly, when a blood clot is detected, it must be quickly and effectively treated.
One method involves surgery to remove the clot and repair the blood vessel. A less invasive method uses thrombolytic drugs to break up, or lyse, the thrombus. This method of treating a blood clot consists of inserting a catheter into the patient's vascular system, preferably near the site of the clot. If the catheter enters the vascular system near the clot, the catheter alone may be used. If, for a variety of reasons, the catheter must be inserted into the vascular system at a distance from the clot, placement of the catheter may be aided by using a guide wire or introducer sheath, which can be used to push and guide the catheter through the vessels or arteries of the vascular system to reach the clot.
Once the catheter is positioned at the site of the clot, a thrombolytic fluid capable of dissolving the clot, such as urokinase or streptokinase, is delivered to the site of the clot by means of the catheter. Conventional catheters have a lumen, i.e., an internal passage, that allows the thrombolytic fluid to flow through the catheter to one or more discharge openings at or near the distal end of the catheter. The discharged thrombolytic fluid then dissolves or lyses the clot, thus removing the danger to the patient.
Not all clots are easily or successfully lysed. Some clots form around arterial lesions, which clots may not be easily lysed or broken up by the thrombolytic fluid and which usually require surgical removal. Additionally, some clots may be extremely thick, extending for a relatively long distance through a blood vessel of the circulatory system. Such a thick clot may require considerable amounts of time and heavy irrigation of thrombolytic fluid to dissolve.
Typically, a guide wire is used in conjunction with a catheter to facilitate placement of the catheter. The guide wire can also serve to penetrate the clot in order to form a passage therethrough so that the catheter can be inserted within the interior of the clot. This helps to ensure that the thrombolytic fluid is concentrated or focused at the location of the clot, since excessive thrombolytic fluid in the bloodstream can have adverse effects on the patient.
After the guide wire has been used to create a narrow passage through the clot, particularly a thick clot, the thrombolytic fluid is released through the one or more openings within the catheter. In the beginning stages of thrombolytic therapy, thrombolysis was carried out using a catheter with a single opening at the distal end of the catheter. Methods employing a simple catheter required movement of the catheter from one end of the clot to the other while dispensing the thrombolytic fluid in order to adequately distribute the fluid over the entire length of the thrombus.
Subsequent attempts have been made to improve the dissolution of blood clots by forcefully injecting a dissolving agent simultaneously along the length of the blood clot. In one such approach, the catheter has a large tip opening and a plurality of small side opening positioned at the distal end of the catheter. The tip opening is used for placement of the catheter. Initially, a long thin guide wire is slid into the vascular system such that the distal end of the guide wire extends through the blood clot. Next, the end of the guide wire outside the body of the patient is received within the tip opening of the catheter. The catheter is then slid over the guide wire, while holding the guide wire stationary, until the infusion holes in the catheter are positioned within the blood clot. Once the catheter is positioned, the guide wire is removed while holding the catheter stationary.
To force the dissolving agent to pass through the infusion holes in the catheter, it is first necessary to block or occlude the large tip opening. This is accomplished by inserting a thin placement wire having an enlarged occluding ball at the distal end thereof into the end of the catheter outside of the patient. The placement wire is advanced until the occluding ball is sealingly disposed at the tip opening. With the placement wire still inside the catheter, the proximal end of the catheter is fluid coupled with a pumping system for injecting the dissolving agent into the catheter and out through the infusion holes thereof. Sufficient dissolving agent is forcefully pumped through the catheter and out against the clot to dissolve the clot.
Although useful, there are several shortcomings associated with the above described catheter system. Most notably, since the catheter tip is located within the body of the patient, it is difficult for the surgeon to determine when the occluding ball of the placement wire is approaching the catheter tip. Although the tip is slightly tapered for seating of the occluding ball, if the surgeon pushes too hard on the occluding wire, the occluding ball can be pushed through the tip opening. If this happens, the catheter and placement wire must be removed and the process of placement repeated.